A wind turbine may comprise a wind turbine tower, a nacelle mounted on top of the wind turbine tower, a rotation shaft rotatably supported within the nacelle, wherein the rotation shaft has one or more rotor blades connected to it. Impacting wind may transfer kinetic energy to the rotor blades which cause the rotation shaft to rotate. The rotation shaft may be mechanically connected to a generator which produces electric energy upon rotation of the rotation shaft. The nacelle may be mounted at the wind turbine tower such that the nacelle may rotate around a vertical axis to direct the rotor shaft and thus the blades in the momentary wind direction which may be denoted as yawing.
For adjusting a transfer of kinetic energy comprised in the wind to the rotation shaft via the rotor blades, the rotor blades may be rotated along a longitudinal axis of the rotor blades. Rotation of the rotor blade around its longitudinal axis (which may lie within a rotation plane being a plane perpendicular to the rotation axis or the rotation shaft) may also be referred to as adjusting a rotor blade pitch angle. Adjusting the rotor blade pitch angle may effect an efficiency or a degree of energy transfer from the wind to the rotor blade and thus to the wind turbine.
Depending on mechanical and/or electronic equipment or components of the wind turbine the wind turbine may be assigned a rated power output or nominal power output. During conditions, where the wind speed is not high enough for the wind turbine to reach the nominal power output the wind turbine may deliver less power output than the nominal power output to a utility grid.
It has been observed that adjusting a pitch angle of a rotor blade in particular in situations, where the wind turbine is operated below the rated power may be difficult. In particular, an optimal power production of a wind turbine at below rated power or below nominal power output may depend on the ability to apply an optimal pitch angle (the pitch angle is the angle between the blade cord line and the rotor plane of rotation which is perpendicular to the rotation shaft) and track the optimal rotor tip speed ratio (the ratio of rotor shaft speed to effective wind speed) at below rated rotational speed of the rotation shaft. Herein, the rated rotational speed of the rotation shaft may also be referred to as nominal rotational speed of the rotation shaft or the nominal speed or rated speed of the wind turbine.
There may be a need for a method and a computing module for determining a pitch angle adjustment signal for adjusting a pitch angle of a rotor blade connected to a rotation shaft of a wind turbine. Further there may be a need for a method for adjusting a pitch angle of a rotor blade of a wind turbine and for an arrangement for adjusting a pitch angle of a rotor blade of a wind turbine, wherein at least some of the above-mentioned problems are reduced.